Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$34.95	7.593%	$37.6038	$37.60	$37.60	$37.60
Purchase #2	$147.52	6.734%	$157.454	$157.45	$157.45	$157.50
Purchase #3	$97.33	10.367%	$107.4202	$107.42	$107.40	$107.40
Purchase #4	$114.92	3.192%	$118.5882	$118.59	$118.60	$118.60
Purchase #5	$47.83	10.185%	$52.7015	$52.70	$52.70	$52.70
Purchase #6	$216.82	5.509%	$228.7646	$228.76	$228.75	$228.80
Purchase #7	$68.85	3.548%	$71.2928	$71.29	$71.30	$71.30
7 purchase totals =	$728.22		$773.8251	$773.81	$773.80	$773.90